How modern science and old-fashioned detective work cracked the salmonella case

— -- The contamination of tomatoes with a rare strain of salmonella has led to the largest outbreak of food-borne illnesses since E. coli in spinach killed five and sickened hundreds almost two years ago.

At least 277 people of all ages in 28 states and the District of Columbia have been sickened; 43 have been hospitalized. A nationwide recall of round, plum and Roma tomatoes has dealt a sharp blow to the $2.7 billion fresh-tomato market, costing the food industry tens of millions of dollars.

But it could have been a lot worse if a red flag hadn't been raised early in the outbreak last month by a public health nurse with good instincts in one of the nation's poorest, most remote regions.

Indeed, health officials say that because the first cluster of patients surfaced on the Navajo Nation in New Mexico, where they are served by a small, close-knit medical community, federal investigators were able to quickly identify the contaminated foods and take steps to contain the outbreak the past two weeks.

After being the first to recognize the signs of an emerging outbreak, the federal Indian Health Service staff played a key role in the search for the tainted food. "It was 21st-century molecular epidemiology and old-fashioned boot leather," says John Redd, the infectious disease branch chief with the Indian Health Service in Albuquerque. "You've got to get out from behind your desk and hit the road sometimes."

Kimberlae Houk has 24 years of experience in public health nursing in the Navajo Nation, the largest reservation in the USA, with lands extending into Arizona, Utah and New Mexico.

Her Shiprock Indian Health Services Unit provides medical care to more than 45,500 American Indians, mostly Navajo, in an area that covers 23 communities in the three states. Homes can be extremely isolated, and many are without telephones.

Houk knew something was up on Monday, May 19, when four people very sick with diarrhea, fever and abdominal cramps showed up at the Northern Navajo Medical Center in Shiprock, N.M.

"A lot of time with these kinds of diseases you get your babies and your grandmas in the hospital," she says. "But in this one we had fit 30-year-olds. And we just don't get 30-year-olds in the hospital with dehydration."

And these people weren't just dropping in at the doctor's office. "We serve a very rural population. They have to drive an hour to the clinic and an hour back. So it's a big deal to come in," Houk says.

With previous experience with outbreaks of measles, whooping cough, hantavirus and even the plague, Houk immediately went into outbreak mode. "We literally drop everything when there's a communicable disease, to protect people."

That day, "We all just ran," says Houk. "We can really get on top of things quickly because all our nurses, our doctors, our clinics, our labs, we're all under the same roof."